The present invention relates generally to hoses and particularly to fuel transport hoses such as fuel filler and fuel filler neck hoses having reduced permeability to fuel vapors. More particularly, this invention relates to fuel hoses constructed from fluoropolymers.
Recent environmental regulations imposed on the automotive industry severely limit the amount of fuel vapor that can permeate from the fuel systems of motor vehicles. Choosing the right polymer to provide high performance, long service life, and reduced permeability of fuel in the fuel systems of automotive vehicles while maintaining costs at an acceptable level has been more difficult for automotive designers than ever before. A particular permeation problem associated with prior art fuel hoses involves the high permeation of fuel vapor along the surface of one of the barrier layers. Typically, fuel transfer and fuel vapor hoses include a butadiene-acrylonitrile rubber inner tubular member and a fluoroplastic barrier layer around the nitrile inner tubular layer as described in U.S. Pat. No. 5,639,528 to Feit et al.; however, such hoses have a high permeability to fuel, high fuel extraction, poor ozone resistance, poor heat aging and poor sour gas resistance. Other hoses have included a fluoroelastomer as the inner wall surface of the hose, but such hoses have a higher permeability to fuel vapors.
Other attempts to produce a fuel filler neck hose with reduced permeability to fuel vapors used a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer liner and a thicker layer of hexafluoropropylene-vinylidene fluoride copolymer or other suitable material as the conductive inner tubular structure. See, for example, U.S. Pat. No. 4,606,952 to Sugimoto and U.S. Pat. No. 5,430,603 to Albino et al. Such hose structures have a tendency to wrinkle on the inner radius of the forming mandrel or pin causing a cosmetic defect.
Accordingly, there is a need for an improved fuel hose that meets present industry standards and is still relatively cost efficient.